Of the three major utility systems available in most buildings, specifically, lighting, plumbing, and heating, ventilation and air conditioning (HVAC), HVAC is the only system that is often not controlled at the individual or room level. For example, there are typically light switches in every room, not one master light switch that controls all of the lights in the building. Similarly, water faucets are typically controlled by individual users. In other words, users do not have to cause the water to run everywhere in the building when they want water in one location. Most traditional HVAC systems, however, have one thermostat that controls many rooms (these multiple rooms combine to form a single HVAC “zone”). Thus, one user often sets the thermostat to a temperature that every other occupant in the same HVAC zone has to accept.
In contrast, some modern HVAC systems allow for the control of temperature in individual rooms, offices or workspaces (each of which may be termed a “microzone”). This is generically accomplished by (1) providing a way to both monitor the actual temperature in each microzone and set the desired temperature for the microzone; (2) providing a way to control the flow of air into the microzone, often through the use of dampers that open or close to allow or prevent air flow; and (3) controlling the HVAC system so that it turns on or off as needed to provide either hot or cold air. It should be noted that modern HVAC systems are often installed as ‘add-ons’ to traditional HVAC systems in order to reduce incremental costs.
Many problems exist, however, with modern HVAC systems. For example, one issue that arises with existing HVAC systems is that an inherent conflict arises when multiple users control a single HVAC system. More particularly, if a user in one microzone wants the system to operate in heating mode, and another user wants the system to operate in cooling mode, a conflict arises between the users. Another issue that arises is that many traditional HVAC systems were not designed to allow for individual control by multiple users. These systems can inadvertently be harmed due to the choices made by individual users of modern HVAC systems. For example, if the vents are closed in a significant percentage of the microzones, the traditional HVAC system may suffer from significant back pressure, and not be able to push enough air over the heating or cooling elements to prevent damage to the system.
Yet another issue that arises with modern HVAC systems is that they are typically installed for one of two primary reasons—increased user comfort, or reduced energy costs. These two user goals are often in direct conflict. For example, to increase comfort, the system may need to be on more frequently than it otherwise would, and may need to rapidly alternate between heating and cooling modes which reduces efficiency. In contrast, if optimized to reduce energy costs, the modern HVAC system may not respond rapidly to individual user requests, significantly decreasing individual comfort compared to traditional HVAC systems.
It is often desirable to be able to prevent air from flowing through an HVAC duct. In fact, in modern HVAC systems it is often desirable for users in each room that is serviced by the HVAC system to have independent control over the flow of air into the room. This is accomplished through the insertion of a mechanical device commonly called a “damper” in the HVAC duct.
A damper is a mechanical device that can be moved between an opened position (allowing the flow of the air through the HVAC duct) to a closed position (preventing the flow of the air through the duct). Some dampers also allow intermediate positions, i.e., partially open or closed. This may allow a limited amount of airflow through the duct. In each case, existing dampers can be controlled directly or remotely, in either a manual or automated fashion.
The majority of dampers currently in use fall into one of the following general categories: butterfly valves, louvers or inflatable bladders. Butterfly valves are typically flat plates that are the same size and shape as the duct. The plate may be mounted on an axle that allows it to rotate around its center. When the plate is rotated so that it is aligned perpendicular to the flow of air, the damper is closed so that no air can pass. When the plate is rotated so it is parallel with the air stream, the damper is open and air flows past the plate with minimal resistance. Dampers that use a louver design have multiple plates that, together, are the same size and shape as the duct and each of which rotates around a separate axle in the center of the individual louver. To open or close the damper, the louvers are rotated around their individual axles. Dampers that use an inflatable bladder design contain flexible membranes that can be filled with air, or some other fluid, to expand the bladder so that it Blocks the flow of air through the duct. The membrane can then be opened to release the trapped air or other fluid, thereby reducing the size of the membrane and allowing the air in the HVAC duct to flow past the damper.
A louver type of HVAC damper is illustrated, for example, in U.S. Pat. No. 6,435,211 to Stone et al. An HVAC damper blade system is illustrated, for example, in U.S. Pat. No. 5,938,524 to Cunningham, Jr. A vane type of damper is illustrated, for example, in U.S. Pat. No. 6,817,378 to Zelczer. Each of these HVAC damper designs, as well as the other damper designs described above, suffers from various shortcomings. For example, the above referenced damper designs may suffer due to power requirements. It is often desirable to have dampers that can operate for long periods of time (multiple years) based on battery power. Damper designs such as butterfly valves and louvers that open in a plane that is parallel to the flow of air, and close in a plane that is perpendicular to the flow of air require significant amounts of energy to be moved between the opened and closed positions as they must overcome significant forces associated with moving air. Additionally, bladders that inflate to Block the air path, and then deflate to open the air path, require significant energy to inflate, especially in larger ducts.
Another problem that arises with such damper designs is noise generation. When opening or closing such dampers in either commercial or residential HVAC applications, it may be desirable to have the damper move between the opened and the closed positions in as quiet a manner as possible to avoid disturbing the building occupants. Implementations of the three above referenced damper designs may suffer from ‘whistling’ noises when changing being moved between the opened position and the closed position. This may be due to air flowing through a partially open damper during the period of time that it takes each of these three basic designs to open or close.
Yet another issue that arises with some of the above referenced damper designs may be excessive back pressure. Many dampers, even in the opened position, partially restrict the flow of air through the duct. If these dampers are installed in multiple ducts in the same HVAC system, the flow of air through the entire system can be affected, even when all dampers are open. This restriction can cause the flow of air to be limited to a level that is below the design level. When this occurs, compressor coils can freeze, and heating elements can overheat, causing major system malfunctions.
Still another issue that arises with the above referenced damper designs may be a space issues. Many HVAC systems are installed in tight spaces, such as, for example, drop ceilings, that do not have the physical space for large dampers. For example, a butterfly valve for a 14 inch duct must be 14 inches high in the open position. These space requirements often force installers to install dampers far upstream of the diffuser in order to accommodate space needs. Upstream installations of such dampers may be difficult, time consuming and costly.
Many dampers that are used in the HVAC industry must be manually opened and closed. This leads to inherent inefficiencies of the HVAC system. In other words, dampers that must be manually moved between opened and closed positions must rely on some intervention and, accordingly, cannot be efficiently used to respond to changes in room temperature. To account for this, some dampers have been powered to move between opened and closed positions, but require the use of AC power. This configuration greatly increases the cost of installation of electrically powered dampers. Accordingly, improvements to HVAC dampering systems are required.